Process for maintaining high level of activity for supported manganese oxide acceptors for hydrogen sulfide



Aug. 23, 1960 J. D. BATCHELOR ETAL 2,950,230

PROCESS FOR MAINTAINING HIGH LEVEL OF ACTIVITY FOR SUPPORTED MANGANESE OXIDE ACCEPTORS FOR HYDROGEN SULFIDE Filed Nov; 8, 1957 2 Sheets-Sheet 1 HIGH SULFUR N m w 2 O 9 ATIFl R A|L\|.|l E E A m m F m R w R DR MO E RN WW EF- FE N LC EC UC GC SA E 0 R q 2 N S w W U T R 0 A W ES I 2 6V L m m IM'I U AL U S 0% F 8 W M 4 S B L c A M L RECYCLE GAS CARBON ACEOUS SOLIDS HOURS OF EXPOSURE TIME AT ELEVATED TEMPERATURE INVENTORS JAMES D. BATCHELOR GEORGE P CURRAN EVERETT GORIN BY AT ORNEY A g 23, 1 0 J. D. BATCHELOR ET AL 2,950,230

PROCESS FOR MAINTAINING HIGH LEVEL OF ACTIVITY FOR SUPPORTED MANGANESE oxxns ACCEPTORS FOR HYDROGEN SULFIDE Filed Nov. 8, 1957 2 Sheets-Sheet 2 3| HIGH SULFUR NET CARBONACEOUS FLUE GAS GAS souos 7 AND so v 20 R m k |2 I E Y IE 10 18 E DESULFURIZATION REGENERATION E 1 x 13 V I? N l9 s SULFIDED 7 g1 ACCEPTOR I -21 I LOW SULFUR I AIR CARBONACEOUS l souos E 32 22 FIRST SECOND STAGE 29 STAGE REACTIVATION REACTIVATIO VESSEL VESSEL AIR 7 124 HOT GASES INVENTORS JAMES D. BATCHELOR GEORGE P. CURRAN EVERETT GORIN TORNEY nited States PROCESS FOR MAINTAINING HIGH LEVEL OF ACTIVITY FOR SUPPORTED MANGANESE OXIDE ACCEPTORS FOR HYDROGEN SULFIDE Filed Nov. 8, 1957, Ser. No. 695,467

11 Claims. (Cl. 202- 31) The present invention relates to a process for maintaining a high state of activity in supported manganese oxide acceptors for hydrogen sulfide. More particularly, it relates to a process for removing sulfur contamination from carbonaceous solid materials by treatment with hydrogen in the presence of manganese oxide-type solid acceptors for hydrogen sulfide.

Such sulfur removal processes for carbonaceous solid fuels have been described in copending US. patent application S.N. 527,705, now US. Patent 2,824,047, filed August 11, 1955, by Everett Gorin, George P. Curran and James D. Batchelor, assigned to the assignee of the present invention. A further process relating to sulfur removal and calcining of carbonaceous solid fuel briquets has been described in copending U.S. patent application S.N. 635,278, filed January 22, 1957, and since abandoned,

and in copending US. patent application S.N. 1,837,

filed January 5, 1960, both by James D. Batchelor, Everett Gorin, George P. Curran and Robert J. Friedrich, both assigned to the assignee of the present invention.

The presence of sulfur in carbonaceous solid fuels limits their use in metallurgical applications. Accordingly, most metallurgical fuels are obtained by employing low sulfur content starting materials, e.g., low sulfur coal is converted to low sulfur metallurgical coke. Sulfur removal processes of the type described in the aforementioned patent applications permit the use of high sulfur content fuels as starting materials for preparing low sulfur content carbonaceous fuels for metallurgical use. For example, the sulfur removal process may be provided as a treatment for the solid residue (termed char) resulting from low temperature carbonization of bituminous coal. Where fluidized low temperature carbonization processes are used, the finely divided, low density, porous char product is particularly amenable to those desulfurization treatments. The desulfurization treatment can be applied to any non-caking carbonaceous solid fuel such as cokm and chars. Coke from coal and hydrocarbonaceous residues (pitch coke), coke breeze, low temperature carbonization char from coal and lignite are exemplary. The processes cannot be applied to caking carbonaceous solid fuels such as caking coal since the thermal treatment encompassed in such processes would cause these materials to become sticky and form coked masses which would bind the acceptor solids, thus preventing their recovery for reuse in the process. Further the resulting coke would be contaminated with the acceptor solids; any sulfur transferred from the carbonaceous fuels to the bound acceptor solids would remain in the solid coke. The processes, however, are applicable to the desulfurization of carbonaceous briquets which may contain caking coal inter alia provided the thermal treatment is conducted to avoid severe caking and accompanying formation of large coke masses.

In the aforementioned copending application S.N. 527,705 solid carbonized carbonaceous fuels are desulfurized by treatment at elevated temperatures in the presence of hydrogen and a solid acceptor for hydrogen are t is the equilibrium value.

ice

sulfide. A preferred acceptor in this process is one containing manganese oxide impregnated on an inert support.

According to that process, carbonaceous solid fuels containing sulfur are mixed with a solid material (termed an acceptor) which is capable of absorbing hydrogen sulfide. The mixture is treated with hydrogen gas at a temperature above about 1100 F. whereby the hydrogen gas combines with the contaminating sulfur toform hydrogen sulfide; the hydrogen sulfide is absorbed in situ by the acceptor. Since the hydrogen sulfide is absorbed almost instantly upon formation, there is only a negligible partial pressure of hydrogen sulfide in the desulfurization zone for inhibiting the reactions whereby sulfur is re moved from the carbonaceous solid fuels. The reaction mixture of solids is separated into (a) product desulfurized carbonaceous solid fuels and (b) the solid acceptor containing accepted sulfur. The acceptor may be regenerated and heated by contact with air to restore its hydrogen sulfide acceptor properties through elimination of previously absorbed sulfur. The heated regenerated acceptor, when mixed with relatively cool carbonaceous solid fuels preferably provides the heat necessary to raise the solids reaction mixture to a desulfurization temperature.

Where the sulfur-containing carbonaceous solid fuel is in the form of finely divided particles (e.g., fluidized low temperature carbonization char, petroleum coke and the like), the acceptor preferably is larger in size to facilitate separation of desulfurized fuel from the sulfided acceptor. When the sulfur-containing carbonaceous solid fuel is in the form of relatively large agglomerate masses, such as briquets, the acceptor preferably is in the form of finely divided fiuidizable size particles to improve contacting efficiency and to facilitate separation of desulfurized fuel from the sulfided acceptor.

carbonaceous solid fuels contain sulfur in at least three forms. Some of the sulfur exists as readily removable sulfur which is organically bound in the carbonaceous fuel. This organically bound sulfur can be removed from the carbonaceous solid fuels rather easily by contact with hydrogen. If the readily removable, organically bound sulfur is represented as -C=S, the desulfurization reaction may be represented as follows:

Some of the sulfur exists as inorganically bound sulfur usually in the form of metallic (principally iron) sulfide. This sulfur may be removed rather readily by treating the carbonaceous solid fuel with pure hydrogen gas. The reaction (assuming iron sulfide) is as follows:

FeS+H H S+Fe The equilibrium ratio for this reaction lI S 2 is very low. Hence small quantities of hydrogen sulfide in the gas phase will inhibit the transfer of sulfur from the solid to the gas. At 1350 F., for example, 0.12 volume percent of hydrogen sulfide in the hydrogen gas At 1600 F., 0.28 volume percent of hydrogen sulfide in the hydrogen gas is the equilib rium value. Thus in order to remove inorganically bound sulfur effectively, the ratio of in the carbonaceous solid fuels.

ceptor is one containing manganese oxide, impregnated and various inorganic sulfides. While this sulfur theoretically can be removed by treatment of the carbonaceous solid fuels with pure hydrogen gas, nevertheless,

.even minute traces of hydrogen sulfide are sufficient to ,inhibit the transfer of sulfur from the solids to the gas. .Removal of the difiiculty removable sulfur is not practicable under feasible processing conditions. 7 V

The ultimate desulfurization which can be achieved at any temperature depends upon the ratio of in the treating gases without regard to the absolute pressure of the reaction system. While greater absolute pressure increases the rate of desulfurization, it

' does not affect the ultimate level of sulfur in the treated solids. In accordance with these findings, satisfactory desulfurization rates may be achieved "at temperatures above about 1100 F. with atmospheric pressure. Higher pressure accomplishes the same desulfurization in shorter time. A preferred pressure range for the desulfurization is about 1 to 6 atmospheres absolute.

It is possible to maintain a low value for the ratio by employing enormous quantities of hydrogen as a treating gas. For example, the use of 1000 molar vol- .umes of pure hydrogen gas in removing one mol of .sulfur would create an environment containing 0.10

volume percent of H 5 in H Alternatively, the ratio on an inert carrier. Suitable carrier materials include silica, alumina and silica-alumina preferably in the form of mullite (containing 75 to 85 percent alumina and the balance silica). V

Acceptors containing manganese oxide are preferably prepared by soaking the inert carrier particles in an aqueous solution of a soluble manganese salt which thermally decomposes to leave a residue of manganese oxide. Manganese nitrate is a preferred soluble salt for this purpose. The concentration of the aqueous solution should be sufiicient to deposit up to about percent by weight of manganese on the carrier. The soaked carrier thereafter is heated to achieve dehydration and decomposition of the deposited manganese salt to the ,c

The reaction of the manganese oxide in the desulfurization treatment is as follows:

MnO+H S- MnS'-|-H O Thus the manganese oxide combines with the generated hydrogen sulfide to form manganese sulfide thereby removing from the vapor phase the hydrogen sulfide hydrogen sulfide and sulfur carbonaceous fuel product.

"t'aining manganese oxide.

tion rate will be observed.

"absorption of hydrogen sulfide occurs.

formed by desulfurization of the carbonaceous solid fuel.

Following suflicient desulfurizing treatment of the carbonaceous solid fuels, the desulfurized fuels are separated from the solid acceptor and recovered as a low As such, the low sulfur carbonaceous solid fuels are suitable for use as. metallurgical fuels.

The separated stilfid'cd acceptor is regenerated by treatment with air to restore the manganese oxide for reuse as follows:

MriS l %O MnOq sb -t heat Thus in the overall process, the sulfur removed from the carbonaceous solid fuels is rejected from the system in the form of sulfur dioxide. So much of the process has been more fully described in the aforementioned application, S .N. 527,705.

The use of H 8 acceptors has been briefly described 'in relation to desulfu'rizatio'n processes for carbonaceous solid fuels. Such H218 acceptors also can be used for removing 'H S from any-gas stream, regardless of source.

For example, elimination of H 5 from petroleum refinery gases, pipeline gas, and the like can be accomplished by passing the "gases over an H S-acceptor con- The H S will be absorbed by the acceptor and the manganese oxide converted to manganese sulfide. The 'sulfided acceptor can be regener- "in this specification refers to a non-oxidizing environment containing H 8 at temperatures where a favorable equilibrium exis'ts'for the reaction The preferred terrip erature range for "H S-absorbing conditions isabout 1100 to 1600" F. The abilityof 4O 7 an acceptor: to react with H S under His-absorbing conditions is an important determinant in the efiiciehcy .of the fundamental desulfurization process.

H Wehave found that repeated use of solid acceptors containing manganese oxide impregnated on silica, alu- .mina or silica-alumina carriers results in deactivation of the acceptor A brief discussion will explain the deactivation phenomenon.

Freshly impregnated acceptor solids will remove hydrogen sulfide gas from a vapor stream in intimate contacttherewith at a determinable rate. Subsequent regeneration of the acceptor by reaction with air willrestore the manganese oxide. However the regeneration necessarily is, conducted at elevated temperatures which .bring. about the deactivation of the acceptor (under 55 ganeseoxide acceptor is employed to remove hydrogen H S-absorbing conditions). ,VVhen the regenerated mansulfide from a gas in contact therewith, a lowerreac- Repeated processing of the acceptor through they sulfiding and regenerating processes will result in further deactivation, i.e., a continued lowering in the rate at which the manganese oxide will remove hydrogen sulfide from a gas in contact b) The rate at which a regenerated acceptor will ab- 'sorb hydrogen sulfide.

The capacity for hydrogen sulfide absorption depends the quantity'of manganese oxide present, whereas the rate at which hydrogen sulfide can be absorbed depends upon a condition which is referred to herein as the acceptors activity under H s-absorbing conditions. Hence the term deactivation refers to a lowering of this activity and the term reactivation refers to an increasing of this activity.

Note that it is possible to have a fully regenerated acceptor (one in which all of the manganese sulfide has been converted to manganese oxide) although that acceptor is deactivated, i.e., the regenerated acceptor will absorb H 8 only at a diminished rate. Should such a regenerated (deactivated) acceptor be exposed to H S- absorbing conditions for a sufliciently long period of time, the quantity of H 8 absorbed by it would depend solely on the quantity of manganese oxide which it contains. A reactivated, regenerated acceptor, on the other band,

would absorb the same quantityof H 8 in a shorterperiod of time.

It is believed that this deactivation of manganese oxide impregnated carriers results from a physical migration of the manganese into the carrier itself. The penetration of the manganese into the carrier may sometimes be accompanied by chemical reaction resulting in the formation of manganese silicates and aluminates. Any manganese thus converted is removed from the cyclic MnOMnS-MnOMnS et cetera reactions.

The principal object of the present invention is to provide a process for reactivating a manganese impregnated acceptor which has been deactivated. A further object is to provide a regeneration process for converting the manganese sulfide of a manganese impregnated acceptor to the desired manganese oxide with minimum deactivation of the acceptor. A still further object is to provide a desulfurization process which employs manganese impregnated acceptors which can be recirculated throughout the process through sequential sulfur absorbing and sulfur elimination without severe loss of activity (under H s-absorbing conditions).

According to the present invention, a portion of the sulfided acceptor undergoing regeneration is subjected to a two-stage combined regeneration and reactivation treatment. In the two-stage treatment, the sulfided acceptor containing manganese sulfide is first contacted with air at a temperature of about 800 to 1100 F. in an attempt to maximize the intermediate reaction.

Some of the manganese sulfide will form manganese oxide directly. The partially regenerated acceptor resulting from the first stage treatment, hence, contains manganese in the form of manganese oxide and manganese sulfate. This partially regenerated acceptor is thereafter contacted with air at a temperature of 1350 to 1600 F. to complete the regeneration as follows:

The conversion of manganese sulfate to manganese oxide is autogenous at temperatures of the order of 1500 F. The regenerated acceptor resulting from the two-stage reactivation treatment includes principally MnO and some higher oxides of manganese such as Mn O and M11 0 Regenerated acceptor which has been reactivated by this two-stage treatment has a fully restored activity under H s-absorbing conditions.

Note that the reactivation process of this invention requires a deliberate cooling of the sulfided acceptor (from the temperature of the desulfurization) prior to a first stage regeneration followed by a heating treatment to complete the regeneration. Normally, a small quantity of carbonaceous material will be commingled with the sulfided acceptor recovered from the desulfurization zone. This carbonaceous material will be transferred from the desulfurization zone to the first and second stage reactivation zones to supply the heat requirements, via combustion, for this higher temperature second stage reactivation.

For a full understanding of the present invention, its objects and advantages, reference should be had to the following detailed description and accompanying drawingsin which:

Figure 1 is a schematic flow diagram illustrating a desulfurization process for carbonaceous solid fuels employing solid acceptors for hydrogen sulfide;

Figure 2 is a schematic flow diagram illustrating the reactivation process steps embodied in the present invention; and

Figure 3 is a graphical representation of the activity loss for manganese oxide-type acceptors according to length of exposure to elevated temperatures.

The generalized flow sheet of Figure 1 illustrates the manner in which an acceptor desulfurization process can be carried out in a continuous manner. IA desulfurization zone 10 receives non-caking carbonaceous solids containing sulfur through a conduit 11 and regenerated acceptor solids through a conduit 12. In this instance, the active ingredient of the acceptor solids is manganese oxide. A hydrogen-rich treating gas consisting essentially of hydrogen is introduced into the desulfurization zone 10 through a conduit 13. Additional gases, consisting of hydrogen gas, are iautogenously produced through devolatilization of the carbonaceous solids at the elevated temperature of the desulfurization zone 10. Under preferred operating conditions the autogeneously produced devolatilization gases will be in sufiicient quantity to provide the full hydrogen requirements for desulfurization so' that ex trinsic hydrogen production is not required.

The desulfurization zone 10 is maintained at a tentperature from about 1100 to about 1600" F. Below about 1100 F., the desulfurization rate is low. Operation above about '1600 F. requires excessive heat and also promotes rapid deactivation of the acceptor. The pressure level preferably is high enough to provide a hydrogen gas partial pressure of at least one atmosphere. A total pressure of from one to six atmospheres is pre ferred.

A typical char (containing sulfur) produced by fluidized carbonization of Pittsburgh Seam coal at 950 F. yields devolatilization gases containing 58.6 percent hydrogen and 24.8 percent methane at 1.3 atmospheres and 1350 F. The same char yields devolatilization gases containing 48.7 percent hydrogen and 32.9 percent methane at 3 atmospheres and 1350 F.

During passage through the desulfurization zone 10, the treating gases remove sulfur from the carbonaceous solid fuels (C=S) +H H S+ (C) forming hydrogen sulfide.

The H S, upon formation, is at once absorbed by the solid acceptor and removed from the gas phase.

Gases are recovered from the desulfurization zone 10 through a conduit 14 and recirculated through conduit 13 for further contact with carbonaceous solids undergoing desulfurization. A net product gas is removed through a conduit 15.

The required residence of carbonaceous solids in the desulfurization zone 10 depends upon the lability of the contaminating sulfur and also upon the level of desulfurization desired. It must be borne in mind that the ultimate sulfur level of the product is determined by the level of H 8 concentration Which the manganese oxide will maintain. Where the hydrogen partial pressure of the treating gases is about one atmosphere or greater, satisfactory desulfurization can be achieved by subjecting the carbonaceous solids to the desulfurization conditions for a period of about three hours or less. Increased absolute pressure, as already pointed out, promotes more rapid desulfurization.

Desulfurized carbonaceous solids are removed from the desulfurization zone 10 as product through a con.

duit 16. Sulfided acceptor is removed through a conduit -17 "and passed to an acceptor regeneration zone 18. "Air is introduced into the re'g'enerationz'one 18 through a conduit 19 to raise the temperature ofthe acceptor through combustion of sulfur along with a portion of the carbonaceous sol-ids commingled therewith and to remove sulfur therefrom through oxidation tosulfur dioxide.

MnS-iog-eMnO i So i-heat The temperature Within theregeneration zone 18 is maintained at about 1300 to 1600 F. Hot-flue gases containing sulfur dioxide are removed from the regeneration zone 18 through a'conduit 20.

Excessive oxidation in the regeneration zone 18 should be avoided in order to restrict'thequantity of higher oxides of manganese produced. Ideally, some of the acceptor solids recovered from the regeneration zone 18 should be in the form of MnS. By maintaining from about 2 to about percent ofthe manganese as MnS after regeneration, the oxides of manganese can be maintained principally in the form of MnO rather than as higher oxides such as Mn O or Mn O The presence of higher oxides of manganese in the desulfurization zone undesirably consumes hydrogen gas without accompanying sulfur removal as Will -be hereinafter described. In general, the amount of oxygen used in the regeneration zone 18 should be within about 20 percent of the stoichiometric quantity, which would be required for oxidizing all of the M118 to MnO according to the equation above.

Regenerated acceptor is returned to the desulfurization zone 10 through the conduit 12 without deliberate cooling to serve therein as a means for removing H S therefrom and to supply the heat requirements thereof.

When the desulfurization process is operated as described with an acceptor comprising manganese oxide impregnated on an inert carrier, deactivation of the acceptor will occur as a result of its thermal exposure. According to the present process as illustrated in Figure 2, the acceptor deactivation may be retarded. In Figure 2, the elements of the process relating to the desulfurization stage bear numerals corresponding to those of Figure 1. Corresponding numerals identify corresponding elements. Regenerated acceptor solids are introduced into the desulfurization stage 10 through a conduit 1 2 Sulfided acceptor solids comprising inert carriers containing manganese sulfide and manganese oxide are recovered from the desulfurization stage 10 through a conduit 17. A portion of the sulfided acceptor is regenerated in the usual'manner by treatment with air at about 1300 to 1600" F. in the regeneration zone 18. Another portion of the sulfided acceptor is withdrawn through a conduit 21, cooled-in a heat exchanger 22, and passed through a conduit 23 into an air conduit 24 for transportation into a first stage reactivation vessel 25 operated 'at a temperature in the range 800 to ll 00 F. The acceptor is contacted with air in the first reactivation vessel 25. Preferably the acceptor is maintained in a fluidized state by means of the transporting air introduced through the conduit 24. At temperatures existing in the first stage reactivation vessel 25, formation of manganese sulfate is promoted in the presence of excess air "as follows:

Some of the manganese sulfide will be converted direct- ,ly to manganese oxide and will liberate sulfur dioxide. The oxygen-depleted air=and sulfur dioxide are removed from the vessel 25 through a-fiuegas conduit 26. Preferably the .pressure maintained within the first stage reactivation vessel. 25 will'be about that employed in the desulfurization zone -10 and preferably will be in the range of l to 6 atmospheres. The'residence time of the acceptor within the first stage reactivation vessel 25 'will 'be selected to maximize the production of manganese 1 term...

such as flue gases.

sulfate and preferably is from about 5 minutes to 2 hours. The partially regenerated acceptor is recovered from the first stage reactivation vessel 25 through a conduit '27 and introduced through a conduit 28 into a second stage reactivation vessel 29 maintained at a temperature in the range of 1350 to 1600 F. The partially regenerated acceptor is contacted therein with hot gases Preferably the acceptor is maintained in a. fluidized state Within the second stage reactivation vessel 29 by means of the transporting gas introduced through the conduit 28. If desired, some air may be introduced into the second Stage reactivation vessel 29 to supply heat therefor by combustion of carbon particles cdrhmingled'with the acceptor solids.

At temperatures above about- 1350" F., manganese sulfate becomes m'olten and tends to undergo autogenous elimination of sulfur dioxide, leaving a residue of manganese oxide as follows:

Mns0 Mno+so +%o Thus that portion of the manganese which had been converted to manganese'sulfa'te in the first stage reactivation vessel .25 is in turn converted to manganese oxide -in the second stage reactivation vessel 29. There is Ta It should be apparent that the hydrogen, consumed in this manner, is utilized non-productively from the process standpoint, i.e., it is consumed without accompanying desulfurization. I

' Formation of these undesirable higher oxides of manganese can be minimized by regulating the residence time of the acceptor within the second stage reactivation vessel 29 and correspondingly controlling the quantity of air therein. The residence period should be suflicient to accomplish nearly complete reversion of the acceptor to manganese oxide without excessive production of the higher oxides of manganese. Satisfactory results are obtained at residence times from about 5 minutes to about 2 hours.

The reactivated acceptor particles are withdrawn from the second stage reactivation vessel 29 through a conduit 31 for recirculation through the desulfurization zone 10 by means of the conduit 12.

These acceptor particles are both regenerated and reactivated. That is, the manganese has been substantially completely converted to the manganese oxide for-m (regenerated) and the acceptor particles have a restored activity for absorbing H 8 (reactivated).

The present invention has been described as a twostage reactivation process for the purpose of explanation. In a preferred embodiment, however, the second reactivation stage is carried out in the main regeneration zone. In this preferred embodiment, the acceptor particles are recovered from the conduit 27 (out of the first stagereactivation vessel25) and introduced through a conduit 32 directly into the regeneration vessel 18. Thus the regenoration vessel 18 functions in the usual way to regenerate the major portion of the recirculating acceptor and also functions as a second stage reactivation vessel for the minor portion of recirculating acceptor which has undergone partial reactivation in the first 'stage reactivation vessel 25.

The preferred embodiment of this invention eliminates the need for an independent second stage reaction vessel. Moreover, the preferred embodiment introduces advantages where the reactivated acceptor contains appreciable quantities of higher oxides of manganese. The higher oxides of manganese may be in part reduced (without consuming hydrogen) by reaction in the regenerator vessel 18 with manganese sulfide supplied from the acceptor entering the regeneration vessel 18 through the conduit 17.

In the case of Mn O the reaction is In general, only a minor portion (from about 1' to 10 percent) of the total acceptor solids undergoing regeneration will be subjected to the reactivation treatment of the present invention. The major portion (from about 90 to 99 percent) of the recirculating acceptor solids will be regenerated in the manner already described.

Figure 3 graphically illustrates the effect of thermal exposure on loss of activity of acceptors impregnated with manganese oxide.

To calculate activity of an acceptor, a weighed batch of the acceptor is placed in a container adapted to confine the acceptor in a bed under fluidizing conditions. A stream of gas having a predetermined composition of hydrogen and H 8 is passed upwardly through the bed of acceptor at a predetermined constant rate as a fluidizing gas. Usually the gas contains about 0.7 percent H S in hydrogen. The fraction of entering H 8 which reacts with the acceptor is measured. Initially substantially all of the entering H S reacts with the acceptor.

grams of H S reacted per hour grams of unreacted MnO in the acceptor bed A freshly prepared acceptor has an activity which can be expressed as unity. The measured activity of any other acceptor under investigation can be compared with that of the freshly prepared acceptor (expressed as unity).

To develop the curves of Figure 3, a mullite carrier impregnated with manganese oxide was used. The carrier contained 4 percent of manganese. Samples of the acceptor were exposed to elevated temperatures for varying periods of time to illustrate the effect of thermal exposure on activity loss. The activity of each sample was determined and compared with that of a freshly prepared acceptor. The activity values (expressed as a percentage of the fresh acceptor activity) are presented graphically in Figure 3 for each temperature level of thermal exposure.

The time required for a 50 percent loss in activity would be about 5 hours at 1600 F., about 6 hours at 1500" F., about 87 hours at 1400 F. and about 210 hours at 1350 F. Since the desulfurization processes are operated with an overwhelming excess of acceptor material, maintenance of a maximum activity level is not requisite. Accordingly, full restoration of activity is not required during each regeneration cycle. Thus only a small portion of the recirculating stream of acceptor is subjected to the reactivating treatment of the present invention. For example, from about 1 to 10 percent by weight of the acceptor solids undergoing regeneration would be exposed to the reactivation treatment of this invention.

To illustrate the eificacy of reactivation of the present process, an acceptor was selected comprising a mullite carrier containing 4.02 percent by weight of manganese.

By virtue of extensive thermal treatment, this acceptor had an activity (under H s-absorbing conditions) only 45 percent of its original activity (under H s-absorbing conditions). About 94 percent of the manganese in the acceptor was in the form of manganese sulfide.

This deactivated acceptor was exposed in its sulfided condition to a large excess of air over the quantity stoichiometrically determined for oxidizing all of its manganese sulfide. The air was passed through a bed of the acceptor under fiuidizing conditions at 975 F. and atmospheric pressure for 63 minutes. Air passed through the vessel at a rate of about 84.5 standard cubic feet per hour per' pound of sulfided acceptor. The acceptor increased in weight by 1.93 pounds per pounds of sulfided acceptor. About 50 percent of the original MnS had been converted to MnSO Thus treated acceptor was thereafter fluidized with air for 30 minutes at a rate of about 83 standard cubic feet of air per hour per pound of acceptor. This second stage reactivation was carried out at 1500 F. and atmospheric pressure. The acceptor decreased in weight by 2.34 pounds per 100 pounds of acceptor (as recovered from the first stage reactivation treatment).

The acceptor was recovered and, on exposure to H 8 absorbing conditions, exhibited a higher activity than the freshly prepared acceptor. Thus an acceptor which through thermal deactivation had retained only 45 percent of its initial activity (when freshly prepared) was reactivated to a condition Where its activity exceeded its initial activity (when freshly prepared). Hence we have demonstrated that the present invention counteracts the deactivation effect accompanying thermal exposure of acceptors containing manganese oxide.

According to the provisions of the patent statutes, w have explained the principle, preferred construction, and mode of operation of our invention and have illustrated and described what we now consider to represent its best embodiment. However, we desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

We claim:

1. In a process employing solid acceptors for hydrogen sulfide comprising manganese oxide impregnated on an inert support for absorbing hydrogen sulfide at temperatures above about 1100 F. to form manganese sulfide, followed by oxidizing the manganese sulfide to manganese oxide by reaction with oxygen at elevated temperatures above about 1300 F., wherein the acceptors suffer a decrease in H s-absorbing activity following said oxidizing, the improvement which minimizes loss of the acceptors activity under H S-absorbing conditions, comprising intimately contacting the manganese sulfide-containing sulfided acceptors with oxygen at a temperature of 800 to 1100 F., converting thereby a substantial portion of the manganese sulfide to manganese sulfate, thereafter heating the thus-treated acceptors to a temperature of 1300 to 1600 F. to eliminate substantially all of the sulfur from the manganese ingredients, and recovering the thus-treated acceptors containing manganese oxide having an increased activity under H s-absorbing conditions.

2. The improvement of claim 1 wherein ,the inert support is selected from the class consist-ing of silica, alumina and silica-alumina.

3. The improvement of claim 1 wherein the inert support is mullite.

4. In the method of removing sulfur from particulate carbonized carbonaceous solids, which comprises preparing an intimate admixture of said carbonaceous solids and particulate acceptor solids comprising inert carriers hav ing manganese oxide impregnated thereon, subjecting said admixture to treatment at a temperature above 1100 F. in the presence of hydrogen gas until a portion of the initial sulfur has been removed from said carbonaceous solids 11 and transferred to said acceptor solids forming manganese sulfide, separating particulate acceptor solids containing manganese sulfide from low sulfur carbonaceous solids, recovering low sulfur particulate carbonaceous solids as product, and restoring the H s-absorbing property of sulfided acceptor solids for recirculation in the process, the improvement in the last-mentioned step comprising contacting a major portion of said sulfided acceptor solids at a temperature of 1300 to 1600 F. under oxidative conditions to remove sulfide sulfur therefrom and reform manganese oxide thereby, contacting 'a'minor portion of said sulfidedacceptor solids at a temperature of 800 to 1100 F. under oxidative conditions to convert a substantial portion of manganese sulfide to manganese sulfate, thereafter heating the thus treated minor portion to 1300 to 1600 F. to eliminate substantially all of the sulfur from the manganese ingredients, and recombining the thus-treated minor portion with the treated major portion for repeated admixing and processing with said particulate carbonized carbonaceous solids.

5. The method of claim 4 wherein the particulate carbonized carbonaceous solids are carbonaceous 'briquets and the inert carriers comprises finely divided fiuidizable size particles of an inert material selected from the class consisting of silica, alumina and silica-alumina.

6. The method of claim 4 wherein the particulate carbonized carbonaceous solids comprise char produced by fluidized low temperature carbonization of caking bituminous coal.

7. In the method of removing sulfur from particulate carbonized carbonaceous solids, which comprises preparing an intimate admixture of said carbonaceous solids and particulate acceptor solids comprising inert carriers having manganese oxide impregnated thereon, subjecting said admixture to treatment at a temperature above 1100" F. in the presence of hydrogen gas until a portion of the initial sulfur has been removed from said carbonaceous solids and transferred to said acceptor solids .forming manganese sulfide, separating particulate acceptor solids containing manganese sulfide from low sulfur carbonaceous solids, recovering said low sulfur particulate carbonaceous solids as product, and restoring the H s-absorbing property of sulfided acceptor solids for recirculation in the process, the improvement in the last- .r-nentioned step comprising contacting amajor portion of said sulfided acceptor solids in a regeneration zone at a temperature of 1300 to 1600 F. under oxidative conditions to remove sulfide sulfur therefrom and reform manganese oxide thereby, contacting a minor portion of said sulfided acceptor solids at a temperature of 800 to 1100 F. under oxidative conditions to convert a'substantial portion of manganese sulfide to manganese sulfate, thereafter introducing the thus-treated minor portion into said regeneration zone to decompose said manganese sulfate to manganese oxide and recovering from said regeneration zone the thus-treated minor portion containing manganese oxide having an increased activity, under H s-absorbing conditions, in admixture with the treated major portion for repeated admixing and processing with such particulate carbonized carbonaceous solids.

8. The method of claim 7 wherein the particulate carbonized carbonaceous solids are carbonaceous bn'quets and the inert carriers comprise finely divided fluidizable size particles of an inert material selected from the class consisting of silica, alumina, and silica-alumina.

9. The method of claim 7 wherein the particulate carbonized carbonaceous solids comprise char produced by fluidized low temperature carbonization of caking bituminous coal.

10. In a process employing solid acceptors for hydro gen sulfide comprising manganese oxide impregnated on an inert support for absorbing hydrogen sulfide at temperatures above about 1100 F. to form manganese sulfide, followed by oxidizing the manganese sulfide to man'- ganese oxide by reaction with oxygen at elevated temperatures above about 1300 F., wherein the acceptors suffer a decrease in H s-absorbing activity following said oxidizing, the improvement which minimizes loss of the acceptors activity under H s-absorbing conditions, comprising intimately contacting a major portion of the manganese sulfide-containing sulfided acceptors with oxygen at a temperature of 1300 to 1600 F. to convert substantially all of the manganese sulfide to manganese oxide,

contacting a minor portion of the manganese sulfidecontaining sulfided acceptors with oxygen at a temperature of 800 to 1100 F., converting'thereby a substantial portion of the manganese sulfide to manganese sulfate, thereafter heating the thus-treated minor portion to a temperature of 1300 to 1600 F. to eliminate substantially all of the sulfur from the manganese ingredients, and recovering the thus-treated minor portion containing manganese oxide having an increased activity under H S- absorbing conditions, and recombining with said major portion.

11. 'In a process employing solid acceptors for hydrogen sulfide comprising manganese oxide impregnated on an inert support for absorbing hydrogen sulfide at temperatures above about 1100 F. to form manganese sulfide, followed by oxidizing the manganese sulfide to manganese oxide by reaction with oxygen at elevated temperatures above about 1300 F., wherein the acceptors suffer a decrease in H S-absorbing activity following said oxidizing, the improvement which minimizes loss of the acceptors activity under H S-absorbing conditions, comprising intimately contacting a major portion of the manganese sulfide-containing sulfided acceptors with oxygen in a regeneration zone at a temperature of 1300 to 1600 F. to convert substantially all of the manganese sulfide to manganese oxide, contacting a minor portion of the manganese sulfide-containing sulfided acceptors at a temperature of 800 to ll00 F., converting thereby a substantial portion of the manganese sulfide to manganese sulfate, thereafter introducing the thus-treated minor portion into said regeneration zone to decompose said manganese sulfate to manganese oxide and recovering from said regeneration zone, in admixture with said major portion, the thus-treated minor portion containing manganese oxide having an increased activity under H s-absorbing conditions.

References Cited in the file of this patent UNITED STATES PATENTS 1,904,582 Watts Apr. 18, 1933 2,756,191 Fritz July 24, 1956 2,764,528 Sweeney Sept. 25, 1956 2,824,047 Gorin et al Feb. 18, 1958 UNITED STATES PATENT OFFICE CERTIFICA'HN 0? i? ECTlQN Patent No. 2,950,230

August 23 1960 James D, Batchelor et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 70, and column 3,

line 6, for "difficulty" each occurrence read difficultly column 6, line 27 for "autogeneously" read autogenously Signed and sealed this 20th day of June 19610 (SEAL) Attcst:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATIUN 0F CORRECTION Patent No. 2,950,230 August 23, 1960 James D. Batchelor et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 70, and column 3, line 6, for "difficulty",

each occurrence, read difficultly column 6, line 27, for "autogeneously" read autogenously Signed and sealed this 20th day of June 1961,

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

4. IN THE METHOD OF REMOVING SULFUR FROM PARTICULATE CARBONIZED CARBONACEOUS SOLIDS, WHICH COMPRISES PREPARING AN INTIMATE ADMIXTURE OF SAID CARBONACEOUS SOLIDS AND PARTICULATE ACCEPTOR SOLIDS COMPRISING INERT CARRIERS HAVING MANGANESE OXIDE IMPREGNATED THEREON, SUBJECTING SAID ADMIXTURE TO TREATMENT AT A TEMPERATURE ABOVE 1100*F. IN THE PRESENCE OF HYDROGEN GAS UNTIL A PORTION OF THE INITIAL SULFUR HAS BEEN REMOVED FROM SAID CARBONACEOUS SOLID AND TRANSFERRED TO SAID ACCEPTOR SOLIDS FORMING MANGANESE SULFIDE, SEPARATING PARTICULATE ACCEPTOR SOLIDS CONTAINING MANGANESE SULFIDE FROM LOW SULFUR CARBONACEOUS SOLIDS, RECOVERING LOW SULFUR PARTICULATE CARBONACEOUS SOLIDS AS PRODUCT AND RESTORING THE H2S-ABSORBING PROPERTY OF SULFIDED ACCEPTOR SOLIDS FOR RECICULATION IN THE PROCESS, THE IMPROVEMENT IN THE LAST-MENTIONED STEP COMPRISING CONTACTING A MAJOR PORTION OF SAID SULFIDED ACCEPTOR SOLIDS AT A TEMPERATURE OF 1300 TO 1600*F. UNDER OXIDATIVE CONDITIONS TO REMOVE SULFIDE SULFUR THEREFROM AND REFORM MANGANESE OXIDE THEREBY, CONTACTING A MINOR PORTION OF SAID SULFIDED ACCEPTOR SOLIDS AT A TEMPERATURE OF 800 TO 